There are some different species, being the best known the flat oyster. Its two halves (valves) of the shell have different shapes. One is extremely concave and the other, conversely, is entirely flat. The inner surfaces of both valves are smooth and usually pearly, white, gray or blue. Its flesh is in white, cream or even gray colour. Its great taste of the sea is what most characterizes and becomes one of the most popular and appreciated shellfish for centuries.